Test Offers Heritability Estimates On New Traits

Swine genetics research is about to take a step into the 21st Century. Traditional measurements of the economically important traits have been redefined in recent years. Traits such as individual feed efficiency and lean growth efficiency have gained prominence as data from the National Genetic Evaluation Program and the Quality Lean Growth Modeling Project have added to the industry knowledge base.Mounting

Swine genetics research is about to take a step into the 21st Century. Traditional measurements of the economically important traits have been redefined in recent years. Traits such as individual feed efficiency and lean growth efficiency have gained prominence as data from the National Genetic Evaluation Program and the Quality Lean Growth Modeling Project have added to the industry knowledge base.

Mounting research has provided efficiency improvements in pig health, facility designs, building design and nutrition programs. Until recently, genetic progress has relied on indirect measurements (backfat, daily gain) on groups of pigs. This indirect method doesn't consider meat quality. The method also reduces rate of genetic progress when sire tests are used and reduces selection accuracy when group measures are assigned to each pig. Heritability estimates for daily feed intake have been based on individually fed pigs but the social interaction of pen groups has made those estimates less useful. Experimental equipment to record individual pig daily feed intake in group pen situations makes direct measurement possible today.

Therefore, as individual feed efficiency and lean growth efficiency are defined and better understood, the desire to determine the heritability levels of these new traits gains urgency. Much as the heritabilities for backfat, loineye area, growth rate and maternal traits were established over the years, researchers are now turning to estimate genetic parameters (heritabilities and genetic correlations) for the new traits - lean growth, carcass composition, fresh loin quality, and loin eating quality.

With this goal in mind, a unique research project has been funded by the National Pork Board in conjunction with the National Pork Producers Council (NPPC) and National Swine Registry to take swine genetics research to the next level. The Genetics of Quality Lean Efficiency Project is designed to help seedstock producers discover more about the animals they are raising and how to most economically make selection decisions to produce more efficient breeding stock in the future.

"These new parameters are tools for scientifically based breeders to use in building better seedstock for commercial producers," states Rodney Goodwin, director of research programs at NPPC.

In the test, a sample half of the carcasses will be separated into lean, fat and bone. Quality and weight measures will be taken on primal and subprimal cuts during carcass separation to increase knowledge of valuing pork carcasses. Genetic parameters of muscle weights will be estimated.

Finally, this project will provide an opportunity to gather genetic material to establish a DNA molecular library linked to measures of economic importance, an investment which could prove invaluable in the future. Many genetic markers are discovered each year but usually only a general idea of their effect is known. Pigs tested in this project will have many measurements of economically important traits.

Testing Protocol The test will involve 1,200 animals, divided between the Duroc and Yorkshire breeds and it will cover two seasons.

In all recent, large-scale genetic evaluations, the Duroc-sired pigs recorded large appetites and grew significantly faster than other genetic breeds or lines. Therefore, Durocs became the logical candidate to research feed intake and growth. The Yorkshire breed, used worldwide, provides a contrast, since they are considered medium-appetite pigs. Both of these breeds have a relatively large genetic pool, enabling the use of many sires in the one-year test period.

Pigs will be delivered to a segregated early weaning (SEW) site at 9 to 20 days of age, thus reducing many health concerns and pretest management differences. Pigs will be identified by electronic eartag and penned in groups of 15. Pens have partially slotted floors. Pigs will begin the test at about 80 lb.

The Feed Intake Recording Equipment (FIRE) system at the Minnesota Swine Testing Station near New Ulm, MN, will be used to record individual feed intakes and allow individual feed and lean efficiency parameters to be calculated. As each pig enters the FIRE feeder, the amount of feed consumed is recorded on a computer.

Test pigs will be entered in sire progeny groups that consist of at least three litters with a maximum of one barrow and one gilt per litter. Participating herds may divide sire progeny groups across testing seasons. There is no restriction on genetic relationships among sires. About 100 sires of each breed could be represented, giving good estimates of genetic parameters for use by all industry breeders. If genetic parameters differ greatly between breeds, the seedstock industry will be alerted to how much additional research funding may be needed to get specific breed/line estimates to make optimum genetic progress.

There will be two testing seasons with two SEW entry dates per season. The first test will start in July 1999. The second testing period will start in early January 2000. Data analysis should provide the industry with results in early 2001.

DNA Reference Points Ancestral documentation and blood samples from all sires and dams will be collected for all test pigs and stored for future DNA analysis. The test pigs will be tested for the halothane (HAL) gene, plus blood and tissue DNA samples will be stored for future research.

Total investment in the project will approach $500,000 with the carcass separation accounting for a major share of the cost. Most of the funding will be provided by checkoff monies allocated by the National Pork Board. Additional funding will be provided by the National Swine Registry.